How prospective memory (PM) weakens with increasing age has been largely debated. We hypothesized that automatic and strategic PM processes, respectively mediated by focal and non-focal cues, are differently affected by aging, even starting from 50-60 years of age. We investigated this issue using a 2 × 2 design in which focal and non-focal experimental conditions were created by varying the conjoint nature of the ongoing task (lexical decision vs. syllable matching tasks) and the PM cue (words vs. syllables). In the whole-brain analysis we found that the left inferior frontal gyrus and the middle cingulate cortex were more activated when young compared to older individuals performed a PM task; moreover, the anterior cingulate cortex was selectively activated during non-focal PM when the cues were words. In a region-of-interest analysis we observed that the medial and the lateral portions of the rostral prefrontal cortex were associated with the focal and non-focal conditions respectively, more in young than in older adults. Our findings provide evidence in support of early age-related differences in automatic/strategic PM functioning.